How to give yourself a heart attack:
1) Find something small, yet important, in your car.
2) Place object in your hat for safekeeping.
3) Get out of car, put on hat, proceed to store.
4) Feel something go down your collar and slide down your back.
Update: I should have been clearer: one may presume that the small, important object was something like a head for a power screwdriver, and as such, was cold and metallic.